Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$149.36	6.740%	$159.4269	$159.43	$159.45	$159.40
Purchase #2	$91.33	7.843%	$98.493	$98.49	$98.50	$98.50
Purchase #3	$97.51	10.301%	$107.5545	$107.55	$107.55	$107.60
Purchase #4	$78.28	4.587%	$81.8707	$81.87	$81.85	$81.90
Purchase #5	$42.69	8.542%	$46.3366	$46.34	$46.35	$46.30
Purchase #6	$38.75	9.375%	$42.3828	$42.38	$42.40	$42.40
Purchase #7	$155.77	4.148%	$162.2313	$162.23	$162.25	$162.20
7 purchase totals =	$653.69		$698.2958	$698.29	$698.35	$698.30